使用Rails应用程序和Chrome浏览器进行缓存

Question

I expect the app should respond with code 304 instead of 200. But even IF-NONE-MATCH equals ETAG it doesn't happen.

I use 'Cache-Control: no-cache' to not store a response in cache to be validated each time. Otherwise Chrome uses it's disc cache, which is unacceptable.

Request:

GET /api/v4/record/11728 HTTP/1.1
Host: host.domain.com
Connection: keep-alive
Authorization: Basic YWRtaW467Uc2Zs0eTIwMTM=
Origin: https://host.domain.com
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/57.0.2987.133 Safari/537.36
Accept: application/json, text/plain, */*
DNT: 1
Referer: https://host-ui.domain.com/some_page
Accept-Encoding: gzip, deflate, sdch, br
If-None-Match: W/"39dcd8467e47701a69c617333f7b6dac"
If-Modified-Since: Thu, 13 Apr 2017 16:09:25 GMT
Name

Response:

HTTP/1.1 200 OK
Access-Control-Allow-Credentials: true
Access-Control-Allow-Methods: GET,POST,PUT,DELETE,PATCH,HEAD,OPTIONS
Access-Control-Allow-Origin: https://host-ui.domain.com
Cache-Control: no-cache
Content-Encoding: gzip
Content-Type: application/json; charset=utf-8
Date: Thu, 13 Apr 2017 16:20:31 GMT
ETag: W/"39dcd8467e47701a69c617333f7b6dac"
Last-Modified: Thu, 13 Apr 2017 16:09:25 GMT
Server: nginx/1.8.1 + Phusion Passenger 4.0.60
Status: 200 OK
X-Content-Type-Options: nosniff
X-Frame-Options: SAMEORIGIN
X-Powered-By: Phusion Passenger 4.0.60
X-Request-Id: ab87433e-62bd-437f-ad7c-0e1d3f95257b
X-Runtime: 0.209121
X-XSS-Protection: 1; mode=block
transfer-encoding: chunked
Connection: keep-alive

In the application common action looks like:

  def action

    record = Model.find(params['id'])

    if stale?(record)
      hard_work_result = to_do_somethig
      render json: {
          success: 0,
          result: hard_work_result
      }
    end
  end

Answer 1

There seems to be a history behind this but short story: gzip is messing with Weak ETags
Weak ETag: ETag: W/"8763458...
Strong ETag: ETag: "8763458...

You can test that this is the problem if you use cURL and disable gzip from Accept-Encoding (or use modheaders in chrome: Disable gzip compression in chrome )

References:

Getting no 304 response in Chrome/Safari but via curl
https://masa331.github.io/2016/01/06/roda-etag-caching-gotcha.html
Weak ETAGs in Rails?

Solution?

When running from nginx itself, the problem did not occur. The first link above suggests that if you are having the problem from within nginx then adding an etag on; after the gzip on; fixes the problem. Specifically though weak etags were not returned. Running from within nginx would seem to be the only option if you want gzip enabled.

my versions

Server: nginx/1.10.2 + Phusion Passenger 5.1.2`)

ii  ruby-rails                      2:4.2.6-1
ii  ruby2.3                         2.3.1-2~16.04

Ive managed to work around the problem when running in passenger standalone by editing the nginx.conf.erb and disabling gzip. To do this, you first need to get the template of the conf file:

passenger start --debug-nginx-config

this will put a file called nginx.conf.erb in your current directory. Then you can edit this file to say:

gzip off;

and then start passenger again with this file

passenger start --nginx-config-template nginx.conf.erb

see here for details of downloading and using the nginx.conf.erb

In either case you should be able to see that weak etags are not returned